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首页> 外文期刊>Journal of Applied Crystallography >A Rietveld refinement method for angular-and wavelength-dispersive neutron time-of-flight powder diffraction data
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A Rietveld refinement method for angular-and wavelength-dispersive neutron time-of-flight powder diffraction data

机译:角和波长色散中子飞行时间粉末衍射数据的Rietveld改进方法

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This paper introduces a two-dimensional extension of the well established Rietveld refinement method for modeling neutron time-of-flight powder diffraction data. The novel approach takes into account the variation of two parameters, diffraction angle 2 and wavelength lambda, to optimally adapt to the varying resolution function in diffraction experiments. By doing so, the refinement against angular-and wavelength-dispersive data gets rid of common data-reduction steps and also avoids the loss of high-resolution information typically introduced by integration. In a case study using a numerically simulated diffraction pattern of Rh0.81Fe3.19N taking into account the layout of the future POWTEX instrument, the profile function as parameterized in 2 theta and lambda is extracted. As a proof-of-concept, the resulting instrument parameterization is then utilized to perform a typical refinement of the angular-and wavelength-dispersive diffraction pattern of CuNCN, yielding excellent residuals within feasible computational efforts. Another proof-of-concept is carried out by applying the same approach to a real neutron diffraction data set of CuNCN obtained from the POWGEN instrument at the Spallation Neutron Source in Oak Ridge. The paper highlights the general importance of the novel approach for data analysis at neutron time-of-flight diffractometers and its possible inclusion within existing Rietveld software packages.
机译:本文介绍了已建立的Rietveld精修方法的二维扩展,该方法用于对中子飞行时间粉末衍射数据进行建模。这种新颖的方法考虑了两个参数(衍射角2和波长λ)的变化,以最佳地适应衍射实验中变化的分辨率函数。通过这样做,针对角度和波长色散数据的改进消除了常见的数据缩减步骤,并且还避免了通常由集成引入的高分辨率信息的丢失。在使用Rh0.81Fe3.19N数值模拟衍射图样的案例研究中,考虑了未来POWTEX仪器的布局,提取了在2θ和lambda中参数化的轮廓函数。作为概念验证,然后将所得的仪器参数化用于对CuNCN的角度和波长色散衍射图进行典型的优化,在可行的计算工作范围内产生出色的残差。通过对橡树岭散裂中子源处的POWGEN仪器获得的CuNCN的真实中子衍射数据集应用相同的方法,可以进行另一种概念验证。本文强调了这种新方法对中子飞行时间衍射仪进行数据分析的普遍重要性,以及可能包含在现有Rietveld软件包中。

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